Technology and the Internet

In the advertising department of SBC Communications, Inc., all of the computers are part of a local area network, connected to one main printer. When an advertising employee prints a document, the job is placed in a queue. It may take several minutes before the document begins to print, due to the number of other print jobs and the complexity of the document. The time (in minutes) until the document starts to print has an exponential distribution with l 5 0.40. Suppose a randomly selected document is sent to the main printer.

a. What is the mean time until the document begins to print?

b. What is the probability that the document will begin to print within 30 seconds?

c. What is the probability that the document will need more than 5 minutes before starting to print?

d. Find a value t such that only 2% of all documents take at least t minutes before starting to print.